This invention relates generally to an electrical connection and more specifically to an electrical connection for an automotive vehicle employing a weld stud.
It is common to arc weld an enlarged circular end of a threaded metal stud onto a sheet metal body panel of an automotive vehicle. Various parts are then inserted upon the single threaded stud and an internally threaded nut is rotationally inserted onto the stud. However, the nut installation is a time-consuming process which often leads to undesirably varying fastening forces.
Conventional threaded weld studs have also been employed as electrical grounding points for a vehicle wire harness to an engine compartment frame or panel. Traditionally, after the stud is welded onto the panel, the vehicle is dipped into an E-coat bath to obtain a corrosion resistant coating and then a spray paint coating is robotically applied. An elastomeric or plastic cap is typically secured onto the stud during the E-coat and paint processes in order to prevent the non-conductive coatings from adhering to the otherwise electrically conductive stud. After painting, the cap is manually removed and then an electrical eyelet is inserted onto the stud. A conventional internally threaded nut is rotated onto the stud by a manually operated torque wrench to secure the eyelet. Alternately, the nut itself can be used in place of the cap during the coating processes, however, the nut must then be removed and then reinstalled after the eyelet is mounted to the stud.
Screws have also been used to retain an electrical eyelet to a grounding panel. Conventional eyelets require upturned tabs to prevent rotation of the eyelets during installation of nuts for the stud construction or when screws are installed. This adds extra cost and complexity to the eyelet.
These traditional constructions are very labor intensive, especially when multiplied by the number of ground studs used in the vehicle. Quality control and repeatability are also difficult to maintain due to under-torquing of the nut or screw, loss of nuts or screws, inadequate prevention of paint in the conductive path, and other intermittent electrical failure concerns, especially when the installation is occurring on a quickly moving vehicle assembly line. It is noteworthy that the paint and E-coat are prone to clogging the threads on these conventional nuts and thereby causing the torque wrench to reach a shut off torque prior to the desired clamp load. Cross threading also causes premature torque wrench shut off.
It is also known to use a pneumatic tool to swage and compress an unthreaded metal nut or sleeve over an arc welded stud in a torque-free manner. This torque-free construction employs a two-part stud, separated by a reduced diameter neck. The tool pulls off the threaded end after the nut is secured to the remaining threaded part of the stud. The nut can be unscrewed and reused. Notwithstanding, it is not believed that such a swaged nut and stud system has been used for an electrical connection or for grounding, especially where a paint prohibiting cap has not been employed.
In accordance with the present invention, a preferred embodiment of a stud electrical connection employs a stud having a patterned external surface and a nut operably secured to the stud in a radially compressive manner. In another aspect of the present invention, installation of the nut onto the stud creates an electrically conductive path between an attached conductive member and a panel. In a further aspect of the present invention, the stud is an electrically grounding weld stud. Yet a further aspect of the present invention creates an electrically conductive path between a stud coated by a generally nonconductive material and a conductive nut. A method of assembling an electrical system using a coated stud and a conductive member engaged onto the stud through swaging is additionally provided.
The stud electrical connection of the present invention is advantageous over conventional constructions in that the present invention achieves reliable electrical conductivity between a coated stud and a nut without the need for extraneous caps or rotational initial assembly steps. Thus, the present invention reduces assembly time and cost while improving electrical reliability in a very repeatable manner. Stud welding feeder reliability is also improved due to the use of longer than typical ground studs prior to severing of the tool gripping end of the stud.
The stud electrical connection of the present invention is further advantageous over conventional devices in that the present invention employs a low cost nut since it does not employ internal threads prior to insertion upon the stud. Engagement of the nut onto the threaded stud does not require any torque upon the nut, thereby reducing the likelihood of inadvertent fracture of the weld between the stud and adjacent panel. Anti-rotational tabs on the eyelet are also not necessary. Moreover, the nut can be unscrewed and reused. Installation of the present invention nut is significantly quicker than conventional pre-threaded nuts, since the traditional nut run-down time is not required. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.